Which description explains the flow of heat?

from cold to hot

from hot to cold

from cool to warm

from cold to warm

According to the second law of thermodynamics, heat flows from hot reservoir to cold reservoir like in heat engines. If work is done on the system, heat can flow from cold to hot reservoir like in refrigerators.

Hence the correct choice is "from cold to hot".

The description it explains to flow of heat it changes from hot to cold.